Repairing an SP404 need help

[Psqwall]

Hello EEV folks
have not posted in a while... I am back with a new project and a request for some help. I recently bought a broken Roland SP404 off a lad who plugged in the wrong power supply and since that time it has not powered on. I immediatly thought blown fuse and rushed over to snatch it up. I got it to my bench and opened it up to find 3 surface mount fuses melted and one processer chip with a little bubble in it. I am guessing that the chip is not effected and if I replace the 3 fuses I will have a working unit. My questions are

1. Where do I purchase the proper fuses for this unit?
2. How do I figure out the proper value I need only one fuse is readable and it reads M2W ?
3. Do you think the chip was effected? I think its just residue from the fuse blast

Here are some pictures of my findings

[SeanB]

Bad news.

Those weren't fuses.........

They were the input voltage regulators, and it was a switching device, it's power switch and the diode, all cooked to death. The bubble on IC13 is fatal damage, but it is replaceable, providing you can get a new one. It was the main RAM for the micro. The EEPROM above it looks like it survived, along with the main microcontroller.

[marshallh]

The bad news is that whatever killed the RAM probably nuked tons of other stuff on there also. Probably the 3v3 was shorted to the input voltage.

[Psqwall]

Thank you all !

So the odds of me repairing this and it being worth it ?

The unit new costs about 400
will the parts cost more than that?

Will I a novice be able to repair all the burnt components?

[Psqwall]

I should say replace not repair the burnt components ?
 

[SeanB]

Sadly no...... Not the cost of the spares ( Ram is cheap, the regulator chips as well) but the tools and knowledge is expensive.

[Psqwall]

Oh well I have a decent iron and a halfway decent scope and most tools

I am asking how hard will it be for me to desolder the 3 input voltage regulators
the IC13 and solder in those 4 parts. I am willing to buy those 4 parts and solder them in to practice. What are the odds of me replacing those 4 parts
will fix the device?  If slim to none do you think that there are other parts I should look for that will be cheap?

My main question is this
I bought this to repair it and get practice and feel all proud of myself when its fixed
now I just feel like a moron lol


I would totally not mind pricing out the 4 parts we know of and if they are under $50 I would buy them and have a go
but what other parts should I be looking for
and most important what website can I buy/price these parts from ?

God I hate new gear ! It's so not repairable !

[SeanB]

If you have the tools and look for a service manual online so you know what the cooked chips are then they will be cheap, and you can desolder them and replace them. The ram is a cheap part, so you will come out under the $50 probably by quite a bit. You might even find them on old dvd writers. If you are willing there are plenty of tutorials here about chip replacement. All involve a lot of liquid flux, a steady hand and good light, which are simple. As you have nothing to lose go for it.

[PA0PBZ]

I wouldn't bet that the only damage done is visible. The voltage regulators are cooked and so is the ram chip, so you have to ask yourself what else will be killed from overvoltage. I think that the chance that the main processor is still ok is less than 50%.

[Psqwall]

Ok so what would be a check list of what I am looking for when it comes to other parts that might have been destroyed ?

What is an estimated parts list and cost list
keep in mind this is a learning project for me

Can I repair a toasted SP404 for under 100 bucks ?

main processor is that a replaceable chip?

Can anyone recommend a good website where I can part out this repair ?
Also I have looked for a service manual online and it just seemed to bring me to sketchy websites
any goto source for Roland products service manuals?

[SeanB]

As the ram died short circuit it likely protected the other chips from damage. You will have to put up the writing or a clearer pic of the crispy chips.

[Psqwall]

OK will do
when I get to my bench tomorrow I will take more pictures that are more clear
I can make a video using a macro lens so all can see. Good news I just downloaded the service manual
and as a reference for anyone else looking to fix a sp404 I am going to post the link here
http://elektrotanya.com/roland_sp404.pdf/download.html

Thanks so much for your help EEVers
I am gonna try and conquer this one first and then get back to my over my head drum machine rebuild
bad news is I have to find a new home for my lab and that might derail my learning

Anyone on here live in NYC ?

[mikeselectricstuff]

Probably worth pulling that RAM off and seeing of the power draw from the rail it runs off (via an external supply) looks sensible, but if that much power got to the RAM, chances are very high other things are smoked as well.

[Psqwall]

Ok
like what other things?
What could get smoked ?
 
Are you all familiar with the Roland SP404 ?

the only thing I think that could make me not go forward with this repair is if the parts
will cost me over $100 bucks or if a whole board is fired
if its a matter of replacing 4 service mount components
or even 10 that are replaceable I think it is worth it

We all can spot 4 things that need replacing
I guess if I open it up further and take more images or video and post it here
we all can better determine if its worth it

Is that safe to say?

Forgive my newbieness  I only just begun repairing audio gear and have fixed a few simple things so far
but I really want to be able to fix things like this so that is why I am so eager

I am not looking to do the imposible though